1. Technical Field
The present invention is generally directed to SHIP1 modulators, as well as to compositions and methods related to the same.
2. Description of the Related Art
In response to extracellular signals, phosphoinositide 3-kinase (PI3K) becomes activated and phosphorylates phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) within the plasma membrane to generate phosphatidylinositol-3,4,5-trisphosphate (PIP3). PIP3 then initiates a cascade of downstream signaling pathways by interacting with pleckstrin homology (PH) domain-containing proteins, such as protein kinase B (PKB, also known as Akt), that regulate cellular activation, function, proliferation and/or survival, depending on the cell type and stimulus (Deane et al., Annu Rev Immunol 22, 563-598, 2004). Cellular levels of PIP3 are normally tightly regulated by the PI3K enzymes, the 5′ SH2 domain-containing inositol phosphatase (SHIP) enzymes SHIP1 and SHIP2, and by the 3′ phosphatase and tensin homolog (PTEN). SHIP1 and SHIP2, dephosphorylate PIP3 to phosphatidylinositol-3,4-bisphosphate (PI-3,4-P2), whereas PTEN dephosphorylates PIP3 to PI-4,5-P2 (Sly et al., Exp Hematol 31, 1170-1181, 2003; Vivanco et al., Nat Rev Cancer 2, 489-501, 2002). Of these, SHIP1 is unique in that its expression is restricted primarily to immune and hematopoietic cells (Sly et al., Exp Hematol 31, 1170-1181, 2003; Damen et al., Proc Natl Acad Sci USA 93, 1689-1693, 1996).
The role of SHIP1 in immune cell homeostasis is shown both by the myeloproliferative syndrome observed in SHIP1−/− mice, as well as the hypersensitivity of SHIP1−/− mice and cells to immune stimulation (Helgason et al., Genes Dev 12, 1610-1620, 1998; Sly et al., Immunity 21, 227-239, 2004). SHIP1 has been shown to mediate signaling from the inhibitory FcγRIIB receptor (Coggeshall et al., Mol Immunol 39, 521-529, 2002), and is important in terminating signal transduction from activating immune/hematopoietic cell receptor systems (Kalesnikoff et al., Rev Physiol Biochem Pharmacol 149, 87-103, 2003).
Diminished SHIP1 activity or expression has been observed in human inflammatory diseases (Vonakis et al., J Allergy Clin Immunol 108, 822-831, 2001) and hematopoietic malignancies (Liang et al., Proteomics 6, 4554-4564, 2006; Fukuda et al., Proc Natl Acad Sci USA 102, 15213-15218, 2005; Luo et al., Zhongguo Shi Yan Xue Ye Xue Za Zhi 12, 420-426, 2004; Vanderwinden et al., Cell Signal 18, 661-669, 2006).
Because dysregulated activation of the PI3K pathway contributes to inflammatory/immune disorders and cancer, intense efforts have been invested into the development of inhibitors of the PI3K enzymes, as well as downstream protein kinases (Workman et al., Nat Biotechnol 24, 794-796, 2006; Simon, Cell 125, 647-649, 2006; Hennessy et al., Nat Rev Drug Discov 4, 988-1004, 2005; Knight et al., Cell 125, 733-747, 2006). The precedent for discovery and biologic efficacy of kinase inhibitors is well established, and a number of promising new PI3K isoform-specific inhibitors have recently been developed and used in mouse models of inflammatory disease (Camps et al., Nat Med 11, 936-943, 2005; Barber et al., Nat Med 11, 933-935, 2005) and glioma (Fan et al., Cancer Cell 9, 341-349, 2006) with minimal toxicities. However, because of the dynamic interplay between phosphatases and kinases in regulating biologic processes, inositol phosphatase activators represent a complementary, alternative approach to reduce cellular PIP3 levels. Of the phosphoinositol phosphatases that degrade PIP3, SHIP1 is a particularly ideal target for development of therapeutics for treating immune and hemopoetic disorders because its hematopoietic-restricted expression would limit the effects of a specific SHIP1 activator to cells that express the enzyme.
To date, a number of small molecule SHIP1 modulators have been disclosed, including sesquiterpene compounds such as pelorol. Pelorol is a natural product isolated from the topical marine sponge Dactylospongia elegans (Kwak et al., J Nat Prod 63, 1153-1156, 2000; Goclik et al., J Nat Prod 63, 1150-1152, 2000). Other reported SHIP1 modulators include the compounds set forth in WO2003/033517, WO2004/035601, WO2007/147251 and WO2007/147252.
While significant strides have been made in this field, there remains a need for effective small molecule SHIP1 modulators. There is also a need for pharmaceutical compositions containing such compounds, as well as for methods relating to the use thereof to treat disorders or conditions that would benefit from SHIP1 modulation. The present invention fulfills these needs, and provides other related advantages.